1. Field of the Invention
The present invention relates to a center feed system for use with a delayed coker system, which may be utilized to dispense residual by-product into a vessel, such as the several types of petroleum feed stocks into a coke drum.
2. Background of the Invention and Related Art
In the hydrocarbon processing industry, many refineries recover valuable products from the heavy residual oil that remains after refining operations are completed. This recovery process is known as delayed coking and produces valuable distillates and coke in large vessels or coke drums. Coke drums are usually in operation in pairs so that when one coke drum is being filled with the byproduct or residual material, the feed may be directed to an empty drum so that the filled drum may be cooled and the byproduct purged from the coke drum, a process known as decoking. This allows the refinery process to operate in a continuous manner, without undue interruption.
The process of delayed coking, and particularly the steps of directing a residual byproduct into an inlet from a feed source and allowing the residual byproduct to be dispensed or disposed within the vessel, comprises utilizing a dispenser that functions to dispose or direct the byproduct into the vessel. FIG. 1 illustrates one type of prior art dispenser or dispensing system common in the industry.
Specifically, FIG. 1 illustrates a cut away perspective view of a dispenser or dispensing system attached or coupled to vessel 2, shown as a coke drum commonly used in the coking industry. Vessel 2 comprises a cylindrical sidewall support body 4 and a lower flange 5. Lower flange 5 further comprises a plurality of bolt holes 7 that are used to receive high strength bolts therein to securely couple vessel 2 to another matching flanged member, such as a de-header valve or an intermediate spool assembly. Attached or coupled to or integrally formed with vessel 2 is a byproduct dispenser, shown as inlet 6, shown in the form of a cylindrical pipe having a flange segment and an opening 8 to allow inlet 6 to be in fluid connection with the interior of vessel 2. As a feed line is appropriately attached to inlet 6, the residual byproduct in the feed line is received through opening 8 in inlet 6, routed through the pipe structure of inlet 6, and dispensed or disposed within vessel 2.
The rather simple design of inlet 6 as the dispenser for the residual byproduct within vessel 2 comprises significant drawbacks. Primarily, due to the pressure within the feed, as well as the high temperature of the residual byproduct, there is significant force within the feed as it enters inlet 6. As a result of this force and the simple, linear design of inlet 6, the residual byproduct is literally shot into or essentially bursts into the interior of vessel 2, hitting the inner side of sidewall support structure 4 opposite the exit area of inlet 6. Even though vessel 2 is pre-heated to a temperature of about 450° Fahrenheit, the incoming byproduct is injected into the drum at about 900° Fahrenheit, and results is the collision of this high temperature, high velocity stream of residual byproduct with the inside surface in sidewall support body 4 that is perpendicular or substantially perpendicular to the direction of the flow of the fast moving, heated residual byproduct. Not surprisingly, this creates or causes significant problems. First, the sudden influx and contact of heated, pressurized material into a stagnant vessel causes stark heat distribution variances throughout vessel 2, namely within sidewall support body 4, and lower flange 5 and the bolts connecting the vessel to another component, such as a de-header valve, throughout the process. The heated residual byproduct is injected into vessel 2 and slams into the opposite sidewall, which instantly begins to heat the immediate and surrounding area of the sidewall. This impact point on the sidewall is the thermal center from which heat is initially distributed to the other adjacent areas of vessel 2. Once the residual byproduct enters the vessel, the opposing sidewall and the surrounding area is heated. Over time, the residual material gathers and builds up inside vessel 2 at a location opposite inlet 6. As this happens, the continuing influx of residual byproduct alternatively impacts the cooled, newly formed coke rather than the sidewall, altering the thermal center. As additional coking takes place, and as additional residual byproduct continues to be injected into vessel 2, the point of impact, and thus the thermal center, continues to move away from the opposing sidewall toward inlet 6, resulting in uneven heat distribution or thermal variance. This process is incapable of providing even heat distribution within the vessel because as each point or location increasing in distance from the thermal center will naturally be relatively cooler.
Uneven heat distribution or thermal variance existing within vessel 2 as a result of the influx of the residual byproduct in the manner described above induces uneven stress distribution within vessel 2, lower flange 5, and the corresponding flanged member coupled to vessel 2, as well as the bolts coupling the two together. As mentioned above, the delayed coking process typically comprises at least two vessels so that while one is being filled the other is being purged of the material therein and prepped to receive another batch of byproduct. Thus, during the off-cycle when a vessel is being purged of its contents it will cool and return to a state of equilibrium. It is this cyclical pattern of dispensing hot residual byproduct into vessel 2 and subsequently hydroblasting the byproduct that leads to the thermal differential and stress within vessel 2. It is this cyclical loading and unloading or stressing and unstressing of vessel 2 that is referred to as thermal cycling. Thermal cycling typically results in the weakening or fatiguing of vessel 2 and its component parts, which leads to a reduction in the useful life of vessel 2.
FIG. 2 illustrates another type of dispenser or dispensing system common in the industry. Specifically, FIG. 2 illustrates a perspective view of a dispenser or dispensing system attached or coupled to vessel 2, shown as a coke drum commonly used in the coking industry. Vessel 2 comprises a cylindrical sidewall support body 4 and a lower flange 5. Lower flange 5 further comprises a plurality of bolt holes 7 that are used to receive high strength bolts therein to securely couple vessel 2 to another matching flanged member 9, such as a de-header valve or an intermediate spool assembly. Attached or coupled to or integrally formed with vessel 2 is a first byproduct dispenser, shown as inlet feed 1, and a second byproduct dispenser, shown as inlet feed 3 positioned opposite and coaxial with one another. Each of inlet feeds 1 and 3 function to dispense byproduct into vessel 2 during a delayed coking process. Although the addition of another dispenser or inlet feed helps to alleviate some of the problems discussed above under FIG. 1, namely the lack of uniform heat distribution, the remedial effect or benefit of two opposing inlet feeds on these problems is only minimal. A significant amount of uneven heat distribution and thermal variance still exists within or throughout vessel 2 because of the inability of the inlet feeds 1 and 3 to dispense byproduct in a controlled and predictable manner. For example, byproduct from each feed inlet 1 and 3 is dispensed into the vessel. If the pressure within each inlet feed are similar, the byproduct from each feed inlet will meet somewhere in the middle and cause byproduct to be randomly displaced within vessel 2. On the other hand, in the even that a pressure differential exists between inlet feeds 1 and 3, then the byproduct will be even more randomly dispensed and the problems of thermal variance increased. Moreover, even if the pressures within each of inlet feeds 1 and 3 are uniform and the byproduct enters vessel 2 at the same or substantially the same time, the depositing and settling of the coke byproduct within vessel 2 is still unpredictable, such that build-up of coke byproduct within vessel 2 could be anywhere, including at the center, along the sidewall, somewhere in between, or any combination of these. As a result, the problems discussed above with respect to the design illustrated in FIG. 1 are equally applicable to the design shown in FIG. 2.
The general trend in the delayed coking industry is towards increased safety, durability, efficiency, and reliability. However, the prior art designs discussed above do not function to meet such goals as these designs are less than efficient and outdated. As such, there is a need to improve how the residual byproducts are injected into the large coke drums.